The ARRA NOT-OD-09-058 encourages expansion of existing research plans to include new populations in a way that will provide growth and employment opportunities. This competitive revision seeks to fulfill these goals by expanding our existing R01 to a novel population of tobacco-using patients with an acute respiratory illness. The Sentinel Events Model (SEM), described in full in the parent R01, is based on the observation that an attempt to quit using an addictive substance is often preceded by the experience of a negative consequence of use, such as a health problem. The goal of the R01 is to better delineate the cognitive and affective mechanisms of action that mediate between a sentinel health event and behavior change milestones. At its core, the SEM consists of three event-related constructs: causal attribution, event- related affect, and perceived event severity. The model specifies how these cognitive and affective constructs influence decision making about substance cessation, behavioral initiation, lapse, and relapse. The parent R01 is applying the SEM to a population of tobacco-using patients experiencing a suspected cardiac event. This competitive revision will cross-validate the applicability of the SEM to a population of patients with an acute respiratory illness. This revision will replicate two out of the three studies presented in the original R01. In the Scale Development Study (Respiratory), we will use a mixed qualitative-quantitative method to create and validate measures of the model's constructs in respiratory patients. Item Response Theory will be used with a sample of 300 participants as an empirically-based method to guide item selection. All participants will be followed for three months after their medical encounter. We will use structural equation modeling and Cox regression to validate the model's predictions. In the Ecological Momentary Analysis (EMA) Refinement Study (Respiratory), we will use the validated scales to guide EMA item construction, and various EMA schedule densities will be examined with a sample of 24 participants to determine the frequency that maximizes compliance. Participants will use cellular telephones provided to them for the purpose of the study to complete the EMA. The Model Testing Study, which is the third study comprising the parent R01, will not be replicated during this revision; instead, it will be the focus of a follow-up R01 that will use the results as preliminary studies. This competitive revision serves to fulfill the NIDA-specific goals of the Recovery Act by adding analyses and populations to the study of comorbid substance abuse-medical illness. The addition of patients with respiratory illness will allow us to examine the applicability of the SEM to a population that may be substantially different in presentation and character from those with a suspected cardiac event. Such an expansion of the model to a second clinical population will allow the establishment of stronger, more reliable evidence about the theoretical underpinnings described in the SEM.